1. Statement of the Technical Field
The invention concerns image processing, and more particularly, systems and methods for fusing image pairs based on modeling of atmospheric and solar illumination.
2. Description of the Related Art
In the field of remote image sensing, two common types of images include panchromatic imagery and multi-spectral imagery (MSI). Panchromatic imagery is obtained by a remote sensing device with a sensor designed to detect electromagnetic energy over one very broad band. This broad band typically includes most of the wavelengths of visible and near-infrared light. Panchromatic imagery has the advantage of offering very high spatial resolution. In contrast, multi-spectral imagery is typically created from several narrow spectral bands within the visible light region and the near infrared region. Consequently, a multi-spectral image is generally comprised of two or more image data sets, each created by sensors responsive to different portions of the optical spectrum (e.g., blue, green, red, and infrared). Multi-spectral images are advantageous because they contain spectral information which is not available from a similar panchromatic image. However, multi-spectral images typically have a lower spatial resolution as compared to panchromatic images.
It is often desirable to enhance a multi-spectral image with the high resolution of a panchromatic image and vice versa. Typically this process is referred to as “fusing” of the image pair. While several methods are available for fusing such image pairs, the resulting fused image from such methods typically results in an inaccurate representation of the color spectrum of the location being imaged. That is, conventional fusion processes tend to distort the color in the images. Accordingly, such methods generally result in fused images which are inadequate for certain types of applications. For example, in the case of image-based material classification, a higher fidelity is generally required that that provided by the conventional fusion of basic color multi-spectral bands (red, blue, green) with a panchromatic band. In particular, additional information from spectral bands that do not significantly overlap with the panchromatic band may be needed for material classification. Even worse, some portions of the visible multi-spectral bands may not be properly represented in the final image due to a limited overlap between the panchromatic band and one or more multi-spectral bands (e.g., blue). Some wavelet-based and statistical approaches are available to include this missing multi-spectral band information, but are generally prone to the introduction of artifacts, sensitive to variations in registration, geographic location, and or atmospheric conditions during imaging, and/or require extensive computations to generate a fused image.